That kind of haphazard configuration control does not bode well for assuaging worries of government customers.

That's an understandable PoV but now that the first stages are starting to be reused I think the rate of change will have to be lowered considerably to limit the number of supply chain variants their ERP system has to track.

Making and tracking N different variants of a part because N different stages were all built slightly differently is a real PITA, in cost, mfg scheduling, machine resources etc. I expect the first stage design will continue to evolve but in more block orientated fashion.

I also think the early recovered stages will have quite short re-use lives to purge the supply chain of too many variants. My instinct is less than 10 flights each at most, but that's a guess.

I think it's very interesting they are talking about "fairing reuse" but not 2nd stage recovery. [EDIT this implies 2nd stage changes can continue at whatever rate they are currently running at and continue to provide hard data for future plans. However it's hard to say how useful this can be without an end goal of fully reusable upper stage, which implies a whole new F9 sized vehicle on LOX/Methane. ]

BFS. The worlds first Methane fueled FFORSC engined CFRP structured A380 sized aerospaceplane tail sitter capable of flying in Earth and Mars atmospheres. BFR. The worlds biggest Methane fueled FFORSC engined CFRP structured booster for BFS. First flight to Mars by end of 2022. Forward looking statements. T&C apply. Believe no one. Run your own numbers. So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.

I don't quite get why everyone in the naysayer camp seems to harp on second stage recovery. They said it's not happening and they're moving on.

Maybe they'll do a Raptor upper stage, maybe they won't...

Logged

"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Making and tracking N different variants of a part because N different stages were all built slightly differently is a real PITA, in cost, mfg scheduling, machine resources etc. I expect the first stage design will continue to evolve but in more block orientated fashion.

I also think the early recovered stages will have quite short re-use lives to purge the supply chain of too many variants. My instinct is less than 10 flights each at most, but that's a guess.

I'd guess even less, maybe at most one reflight for most of them, and none for the oldest ones. When they need to pick a core to refurbish, they will pick the one that's in the best shape and needs the least work. After that the next best, and so on. The newly built cores will naturally be at the top of this list, since they have the most things already fixed, and are closest to the current configuration. The oldest cores will never be used, as enough newer cores are available.

I'm not shocked by any of this, they are in block transition (multiple blocks) to block 5.

A view this flight as an initial proof of concept rather than a view of how every refurbishment will be in the future.

Given this is the first time a first stage has been reflown ever this must be viewed as an extreme outlier. According to the story 1021 first flew April 8th 2016, close to a year ago.

I don't think anyone believes it has taken SX close to whole year to refurbish it. I suspect most of that time will have been spent working out and documenting the refurbishment procedure (including deciding which processes are unique to this stage, and which applicable to it and all future ones).

How much the actual elapsed time (and staff) needed to do a full refurb will remain anyone's guess.

I don't quite get why everyone in the naysayer camp seems to harp on second stage recovery. They said it's not happening and they're moving on.

Maybe they'll do a Raptor upper stage, maybe they won't...

Only die hard fanbois have been talking about second stage recovery.

The rest of us took Musk at his word and moved on long ago.

Logged

BFS. The worlds first Methane fueled FFORSC engined CFRP structured A380 sized aerospaceplane tail sitter capable of flying in Earth and Mars atmospheres. BFR. The worlds biggest Methane fueled FFORSC engined CFRP structured booster for BFS. First flight to Mars by end of 2022. Forward looking statements. T&C apply. Believe no one. Run your own numbers. So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.

That kind of haphazard configuration control does not bode well for assuaging worries of government customers.

If only NASA and the USAF were deeply involved with SpaceX as part of the certification processes being run by both instituations...

As noted above, this probably explains some of NASA's concerns following the CRS-7 situation.

Disagree all you like, but configuration control issues have led to more than one fatal aviation incident (both civil and military). And these are well-established fields with incredibly meticulous certification procedures. Those procedures exist for a reason: because when people don't document what they did and things go bad, you can never be certain you actually figured out why they went bad - unless, as had happened more than once - you discover parts in the debris that weren't supposed to be there, or evidence of prior repairs or construction that weren't supposed to be have been done that way.

However, adding more and more checks comes with a cost, which is snowballing ever-so-slightly. And if you do not pay attention to this snow-balling, you may inadvertently end up with a situation when replacement of a single bolt requires one person to do the work and ten people documenting it, cross-verifying it, then documenting and cross-verifying the process of documenting.

Not only it makes the process much slower and more expensive, it also makes people working on the hardware averse to the changes (since they need to do tons and tons of paperwork for each).

And then you find your rocket engine designer, totally frakked off at the fact his "rocket design" work entails only doing endless paperwork, quit you company to work for some ridiculous startup.

And then this startup's rocket whooshes past you, while you stare at the glowing letters on the wall: "Prepare to Become Obsolete".

That kind of haphazard configuration control does not bode well for assuaging worries of government customers.

If only NASA and the USAF were deeply involved with SpaceX as part of the certification processes being run by both instituations...

As noted above, this probably explains some of NASA's concerns following the CRS-7 situation.

Disagree all you like, but configuration control issues have led to more than one fatal aviation incident (both civil and military). And these are well-established fields with incredibly meticulous certification procedures. Those procedures exist for a reason: because when people don't document what they did and things go bad, you can never be certain you actually figured out why they went bad - unless, as had happened more than once - you discover parts in the debris that weren't supposed to be there, or evidence of prior repairs or construction that weren't supposed to be have been done that way.

However, adding more and more checks comes with a cost, which is snowballing ever-so-slightly. And if you do not pay attention to this snow-balling, you may inadvertently end up with a situation when replacement of a single bolt requires one person to do the work and ten people documenting it, cross-verifying it, then documenting and cross-verifying the process of documenting.

Not only it makes the process much slower and more expensive, it also makes people working on the hardware averse to the changes (since they need to do tons and tons of paperwork for each).

And then you find your rocket engine designer, totally frakked off at the fact his "rocket design" work entails only doing endless paperwork, quit you company to work for some ridiculous startup.

And then this startup's rocket whooshes past you, while you stare at the glowing letters on the wall: "Prepare to Become Obsolete".

Sure. But none of that invalidates anything I actually wrote. That's entirely not the point.

I'm not contradicting you. I'm pointing out there is a drawback in having way too much configuration control.

No, actually you're not. It's quite possible to have excellent configuration control and do it efficiently. The issue I have (*) here is that it wasn't done CONSISTENTLY. Consistency, repeatability, and frequent repetition is the key to efficiency.

(*) Assuming arguendo the kid's story is, in fact, accurate. I'm not entire sure he wasn't exaggerating for effect.

I'm not contradicting you. I'm pointing out there is a drawback in having way too much configuration control.

No, actually you're not. It's quite possible to have excellent configuration control and do it efficiently. The issue I have (*) here is that it wasn't done CONSISTENTLY. Consistency, repeatability, and frequent repetition is the key to efficiency.

Elon just mentioned possibly trying for second stage recovery in his press conference...

I've just skimmed the SES10 webcast. Musk has a short segment. [EDIT re-checked it. He talks about booster reuse and how not throwing the whole thing away every launch saves money. There is no mention of upper stage reuse. It runs about 3 mins round 40+ mins into the cast ][EDIT in the interests of completeness Shotwell said the last planned spin of the F9 design is to give 10 reuses, suggesting all the 1st stages till then (sometime later this year) will have less than 10 flight design lives. TBH 10 flights seems quite low, and a long way from "aircraft like." I would have guessed a generation after that with a longer life, but in truth only SX know (because they've had real hardware to take apart) what cumulative damage is done during the whole launch/sep/land/refurb cycle ]Has he given another longer press briefing?

« Last Edit: 03/31/2017 01:05 AM by john smith 19 »

Logged

BFS. The worlds first Methane fueled FFORSC engined CFRP structured A380 sized aerospaceplane tail sitter capable of flying in Earth and Mars atmospheres. BFR. The worlds biggest Methane fueled FFORSC engined CFRP structured booster for BFS. First flight to Mars by end of 2022. Forward looking statements. T&C apply. Believe no one. Run your own numbers. So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.

The initial quoted Reddit post by the alleged intern that indicated parts were found during refurbishment that apparently didn't even exist at the time of assembly; that means configuration control was not applied consistently during the flow from assembly to flight prep to launch, because - by definition of the term - the use of said part would not have come as a surprise during refurbishment of the stage.

Quote

So... based of on an iffy source, you make the worst assumption?

Go back and read my initial quote - in context - without the defensiveness for all things SpaceX. It's quite possible to be a vehement fan and still worry about flaws in the processes used to achieve their goals. If what the kid said is accurate, their processes were flawed. People are flawed; the processes are supposed to work around those human flaws.

I've just skimmed the SES10 webcast. Musk has a short segment. [EDIT re-checked it. He talks about booster reuse and how not throwing the whole thing away every launch saves money. There is no mention of upper stage reuse. It runs about 3 mins round 40+ mins into the cast ]

I'm just getting out of work and haven't been able to watch the Q&A session. According to Jeff Foust, Elon said might be "fun to try a Hail Mary" and recover the second stage. Chris Gebhardt relayed the same message here on NSF:

But then the only thing left is the upper stage, which we didn't originally intend for Falcon 9 to have a reusable upper stage, but it might be fun to try like a hail mary, and you know. What's the worst thing that can happen? It blows up. You know, it blows up anyway. [Martin Halliway chimes in humorously. "We need to discuss this."]

(Fairing recovery talk started at 12:05 when a guy walked in and showed Elon a photo of the floating fairing, but that's another thread.)

Key info from Elon at the press conference on booster 21 refurbishment for the SES-10 flight:

Quote

With this being the first reflight we were incredibly paranoid about everything. So we sort of, the core airframe remained the same, the engines remained the same but any auxiliary components we thought might be slightly questionable we changed out.

Now our aspiration would be zero hardware changes, reflight in 24 hours the only thing that changes would be we reload propellant.

I'm just getting out of work and haven't been able to watch the Q&A session. According to Jeff Foust, Elon said might be "fun to try a Hail Mary" and recover the second stage. Chris Gebhardt relayed the same message here on NSF:

EDIT: Found it. Around 14:20 in this video of the press conference Elon mentions potentially trying for reuse of the second stage.

I heard that too. Yes Musk is remains interested in full reuse. If you've just spent 15 years and about $1Bn on reusability you're not going to let go easily.

I'm guessing if some of his team come up with a (not too expensive) plan to give F9 US reuse a go with at least a 1 in 10 chance of success he'd give it a go, if they can find a customer willing to take the risk.

Otherwise F9 US reuse is dead as a dodo.

Having started to watch the actual press conference, rather than the launch coverage Musk mentions they are looking at a life of 10 first stage flights with no refurb but 100+ with work being done.

That suggests 10 flights is how long the TPS is good for without any repair or replacement. Beyond that it's certain it will burn through somewhere.

What I'd really like to know is what (if any) is the cumulative fatigue to the main structure caused by the hoverslam landing.

I keep thinking of the old saying that boxers and football players go in the knees first.

Logged

BFS. The worlds first Methane fueled FFORSC engined CFRP structured A380 sized aerospaceplane tail sitter capable of flying in Earth and Mars atmospheres. BFR. The worlds biggest Methane fueled FFORSC engined CFRP structured booster for BFS. First flight to Mars by end of 2022. Forward looking statements. T&C apply. Believe no one. Run your own numbers. So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.

I'm guessing if some of his team come up with a (not too expensive) plan to give F9 US reuse a go with at least a 1 in 10 chance of success he'd give it a go,

Otherwise F9 US reuse is dead as a dodo.

Reuse is not the only reason to try recovering a second stage given the Mars goal. Just learning how to get one back down in a small integer number of pieces, compared to burning up, would be valuable information

Working my way through the press conference video (had some sound problems)

Around 32mins in says they are switching to forged Titanium alloy for the grid fins from TPS coated Aluminum and they are going to be the worlds biggest Ti forgings.

This is an unusual choice given that there are very few really big presses EG 50 000 tons. They are used for things like the rotor hubs of really big helicopters, or nuclear reactor pressure vessels. They're very specialized and it's an odd choice given getting a mfg schedule on them is likely to be quite tricky.

It's even more so given that Ti alloys are quite attractive for diffusion bonding (the oxide layer is soluble in Titanium), so making up a grid structure in a vacuum furnace (even a big one) would be quite viable.

[EDIT They payoff seems to be that with these new fins will give the F9 a L/D of 1, presumably in the hypersonic regime. Given that this is a bottom heavy (very) blunt body that's potentially pretty high]

« Last Edit: 03/31/2017 10:09 PM by john smith 19 »

Logged

BFS. The worlds first Methane fueled FFORSC engined CFRP structured A380 sized aerospaceplane tail sitter capable of flying in Earth and Mars atmospheres. BFR. The worlds biggest Methane fueled FFORSC engined CFRP structured booster for BFS. First flight to Mars by end of 2022. Forward looking statements. T&C apply. Believe no one. Run your own numbers. So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.